Radio receiving system



Feb. 28, 1933. M. M; EELLS 1,899,025

RADIO RECEIVING SYSTEM Filed Nov. 11, 1926 2 Sheets-Sheet 1 Mi/fo/z Nerwin Eel/s Feb. 28, 1933. M. EELLS 1,899,025

RADIO RECEIVING SYSTEM Filed Nov. 11. 1926 2 Sheets-Sheet 2 Nl'lfo/L Mer'win Eel/s Patented Feb. 28, 1933 UNETEE STATES PATENT orricE MILTON MERWIN' EELLS, F CHICAGQ, ILLINOIS, ASSIGNOI'L, BY MESH E ASSIGNMENTS,

TO WILLIAM TUENOR LEWIS, OF B-ACINE, WISCONSIN RADIO RECEIVING SYSTEM Application filed. November 11, 1926. Serial No. 147,698.

vThis invention relates to a radio receiving system.

It is well known that in wireless receiving systems. that radio frequency ener y creates considerable trouble in the audio frequency amplifiers. Various attempts have been made to lessen this disturbance, and it is customary to provide a bypass condenser from the plate directly to the filament to offer a path of comparatively low reactance to radio frequency current, but this condenser has been found to bypass a considerable portion of the higher frequency audio currents which causes objectionable distortion. In addition to this, some of the radio frequency energy will follow a path through the audio frequency transformer and create more or less disturbance. Various other attempts have been made to lessen the eifect of this radio frequency energy in the audio frequency circuits, but these attempts have not proven satisfactory.

This invention is designed to overcome the defects noted above and. objects of this invention arev to provide a tuned resonant circuit associated with the audio frequency circuits in such a manner as to prevent the passage of the radio frequency energy to the audio amplifiers, either by stopping the radio frequency energy on its way to the audio frequency amplifiers, or else by bypassing the radio frequency energy so that it does not arrive at the audio frequency amplifiers.

More specifically, objects of this invention are to provide a novel radio receiving circuit in which either one or more resonant portions are provided, such portions being resonant to radio frequency energy and acting either as a means for stopping the passage of such energy or as a means for bypassing such energy, these various resonant portions ofthe audio circuits being tuned to the radio frequency waves.

This invention further contemplates the provision of a gang control for the several tuning elements for operation from the usual tuning elements or individually.

Embodiments of the invention are shown F in the accompanying drawings in which:

Figure 1 is a diagrammatic view of a portion of the audion circuit of a wireless receivmg system, in which parallel resonant circuits are provided for suppressing the'radio frequency energy;

Figure 2 is a diagrammatic view show- 111g means for bypassing the radio frequency energy and also means for suppressing such energy by the use of a tuned circuit;

Figure 3 is a View of a further form of the invention in which a tuned bypass is provided in addition to the means for suppressing the radio frequency energy;

Figure 4 is a further form of the invention showing means for bypassing the radio frequency energy and choking out the radio freq uency energy in the transformer circuit;

Figure 5 is a further view of another mode of accomplishing this result;

Figure 6 is a View showing onearrangement in which this invention may be applied to the grid circuit of an audio frequency amplifier;

Figure 7 is a View similar to Figure 6 showing, however, a resonant bypass in the grid circuit of the audio ampli 'er;

Figure 8 shows a combination of means for suppressing the radio frequency energy in the grid circuit and means for bypassing such energy;

Figure 9 is a view of the audio amplifier portion of a radio receiving circuit in which the plate circuits and grid circuits are both supplied with resonant means for suppressing the radio frequency energy and also resonant bypass means for such energy.

Referring to the drawings, particularly Figure 1, it will be seen that a. pair of vacuum tubes'l and 2 have been provided and that these tubes have their plates connected through the primaries 3 and 4 of audio frequency transformers to the plate battery 5. The filament circuits are supplied from the battery 6 and controlled in any suitable manner, as by means of the variable resistance 7.

In order to prevent the radio frequency energy from finding its way through the plate circuits, an inductance coil 8 is provided in the plate circuit of each tube, and is bridged by a variablecondenser 9. It may be found desirable to use only one of these 100 parallel resonant circuits but, if desired, any number may be employed, as indicated in Figure 1.

These resonant circuits are tuned to the incoming wireless Waves and offer theoretically infinite impedance to the passage of this energy. In practice, it has been found that these parallel resonant circuits stop the passage of the radio frequency energy and prevent its passage to the audio frequency amplifying tube.

This same result could be accomplished by the system shown in Figure 2. In this form, it will be seen that the vacuum tube has its plate connected through the inductance coil 11 to the primary 12 of the audio freuenc'y transformer. A second coil 13 1s dlosely'coupled to the coil 11, and 1s bridged by a variablecondenser 14. Obviously, tuningthe resonant circuit, composed of the co l 13 afh'dtlie condenser 14, will cause the coil 11 to offer an enormous impedance to the pasof radio frequency energy.

addition to this construction, a bypass condenser-"15 is connected to the plate and the filament 'of the tube 10 to bypass the radio fr uency energy.

l his general idea may also be carried out I bythe construction illustrated in Figure 3 in which the inductance coil 16 in the plate circuitbf the tube 17 is brid ed by a variable condenser 18. However, tile bypass circuit between the plate and the filament of the tube 17 is composed of an inductance coil 19 and a variable condenser 20; The bypass circuit and the parallel resonant circuit are both tuned to the incoming radio frequency waves. The bypass circuit offers the minimum unpedance to the passage of the radio frequency energy from the late circuit to the filament, while the paralle resonant circuit offers the maximum impedance to its passage.

It is, of course, to be appreciated that the parallel resonant circuit for stopping the passage of the radio frequency energy n the plate circuit may be placed after the primary of the transformer, if desired.

In the form of the invention shown in Figure 4, the same bypass circuit is provided for the radio frequency energy as that described in connection with Figure 3 by means of the coil 21 and the variable condenser 22 connected between the plate and the filament of the tube 23. However, a radio frequency choke 24 is connected in the plate circuit and may be located either before the primary of the audio frequency transformer 25, as shown in Figure 4, or else after such primary. This choke holds back the radio frequency currents in the plate circuit, the tuned circuit consisting of the coil 21 and condenser 22 bypassing the radio frequency currents.

It is to be understood further that the radio frequency choke could be replaced by a parallel resonant circuit, if desired, as shown in Figures 1, 2, and 3.

In the form of the invention shown in Figure 5, the plate of the tube 26 is connected through the primary 27 of the audio frequency transformer to a parallel resonant circuit composed of the coil 28 and the variable condenser 29. A bypass condenser 30 is bridged across the plate circuit and the filament of the tube.

Obviously, this same inventive idea can be carried out with regard to the grid circuit of the tubes. For example, as shown in Figure 6, the tube 31 has its grid connected throu h the parallel resonant circuit composed of t e coil 32 and the variable condenser 33 to the secondary 34 of the audio frequency transformer, and from thence to the filament of the tube. This construction suppresses the passage of the radio ener y to the filament of the audio frequency amp ifying tube. Clearly, the parallel resonant portion of the circuit could be placed either before or after the primary of the transformer.

In the form shown in Figure 7 the audio frequency amplifying tube 35 has its grid and filament connected to the secondary 36 of the audio frequency transformer. However, the filament an grid are bridged a series resonant circuit composed of the coil 37 and the variable condenser 38.

In the form of the invention shown in Figure 8, both of the previously described schemes or constructions are followed. In this case, the grid of the audio frequency amplifying tube 39 is connected to the secondar 40 of the audio frequency transformer. This transformer has its other terminal connected to the filament of the tube through the parallel resonant circuit composed of the coil 41 and the variable condenser 42. However, the filament and grid are bridged by the series resonant circuit consisting of the coil 43 and the variable condenser 44.

Thus, in this circuit the maximum impedance is offered to the passage of the radio frequency energy through the grid circuit, but any energy that may inadvertently arrive at the grid will be bypassed to the filament of the tube by means of the series resonant circuit and, consequently, the radio frequency energy will not affect the operation of this audio frequency tube.

Figure 9 shows a combination of the means for both suppressing and bypassing radio frequency energy in both the plate and grid circuits of the tubes. Forexample, the tube 45 has its plate connected through the inductance coil 46 to the primary 47 of the audio frequency transformer. The coil 46 is bridged by a variable condenser 48. A series resonant circuit is connected between the plate and the filament of the tube 45 and consists of the coil 49 and the variable condenser 50.

The secondary 51 of the audio frequency transformer is connected to the filament and grid of the next tube 52. In this grid circuit a coil 53 is interposed and is closely coupled to a coil 5%, such lattercoil being bridged by the variable condenser 55. Further, a series resonant circuit bypasses the radio frequency energy from the grid to the filament of the tube-52. This circuit consists of the coil 56 and a variable condenser 57.

Although certain specific forms of the invention have been disclosed, it is to be understood that various combinations of the several circuits may be made, provided the spirit of the invention is not departed from. For instance, other combinations of grid and plate circuit impedances may be made than those actually disclosed, by utilizing other forms of the invention disclosed in the drawings and combining them in a manner similar to that shown in Figure 9.

It is to be understood that the condensers 1 my be either individually or gang controlled for tuning the resonant portions of the circuits to the incoming radio Waves. Further, these condensers may be controlled by one of the main tuning controls (not shown) of the system.

It will be seen that means have been pro vided in the various audio frequency circuits for offering maximum impedance to the passage cf radio frequency energy, and also that means have been provided Which offer minimum impedance to the radio frequency energy and bypass it so that it does not affectthe operation of the tubes.

Although the invention has been described in considerable detail, such description is intended as illustrative rather than limiting as the invention may be variously embodied and as the scope of such invention is to be determined as claimed.

I claim:

1 In a radio receiving system, the combination of a plurality of tubes having the plate circuit of one tube coupled to the grid circuit of the succeeding tube, one of said circuits having a tuned resonant impedance interposed therein to prevent the passage of radio frequency energy to the grid of the succeeding tube, said impedance being tuned to the frequency of the received energy and a bypass from the filament of one tube to one of said circuits, said bypass permitting the free passage of radio frequency energy.

2. In a radio receiving system, the combination of a plurality of amplifying tubes, the plate circuit of one tube being coupled to the grid circuit of the succeeding tube, said circuits each extending to the filament of its corresponding tube, a resonant tuned portion forming a portion of said'circuits, and a resonant bypass extending from the filament to the plate of one of said tubes, said resonant bypass being tuned to the frequency of the received energy.

3. A radio receiving system comprising a plurality of amplifying tubes having the plate circuit of one tube connected through an audio frequency transformer to the grid circuit of a succeeding tube, the plate circuit and the grid circuit having tuned resonant means for suppressing the passage of radio frequency energy, the plate of one tube being bypassed to its filament by tuned resonant means, said lastmentioned means being tuned to the frequency of the received energy.

4t. A. radio receiving system comprising a plurality of amplifying tubes having the plate circuit of one tube connectedthrough an audio frequency transformer to the grid circuit of a succeeding tube, the plate circuit and the grid circuit having tuned resonant means for suppressing the passage of radio frequency energy, the plate of one tube being bypassed to its filament by tuned resonant means, and the grid of the succeeding tube being bypassed to its filament by tuned resonant means, each resonant means being tuned to the frequency of the received energy.

5. In radio receiving system, the combination of a plurality of tubes, the plate circuit of one tube transmitting energy to the grid circuit of a succeeding tube, a parallel resonant instrumentality interposed between the plate of said-first mentioned tube and the grid of said second mentioned tube, and a series resonant instrumentality interposed between the plate and filament of said first mentioned tube, said instrumentalities being tuned to the same radio frequency.

In testimony that I claim the foregoing I have hereunto set my hand at Chicago, in the county of Cook and State of Illinois.

MILTON MERWIN EELLS. 

